Mouthbrooders: Collecting and Raising the fry
Mouthbrooders: Collecting and Raising the fry
Written by Tuesday, 09 April 2002 02:00
Raising the fry of any fish is a very pleasing and rewarding procedure. Although it is perhaps one of the most difficult, delicate and painstaking parts of fishkeeping, very few hobbyists will ever complain about it. The mere fact that you have fry to care for means that you succeeded in providing this particular species with almost what it needed to feel comfortable so as to spawn and then carry the eggs and fry.
There are many ways fish use to spawn and then take care of their fry but this article will focus on Malawi cichlids which show the most advanced form of parental care; mouthbrooding. This article will just mention some facts that come from my experience and will hopefully help other fellow hobbyists to avoid some pitfalls. Cichlids from Lake Malawi do their best to help us to raise their fry. Instead of laying thousands of eggs and then guard them in the tank (causing all sorts of trouble) they produce a limited number of eggs (150-180 at most, in large, mature species). This is because mouthbrooding ensures that their fry, when released will be already 0.8-1 cm in length and far better "equipped" to cope with life. In contrast, other cichlids produce thousands of eggs just to compensate for very high mortality rates. It worths mentioning that in a recent article in "Cichlid News" (April 2000), Ron Coleman refers to a total loss of 68 broods out of 87 spawning of Neolamprologus mondabu (Lake Tanganyika). This shows the importance of mouthbrooding for the fish.
Mouthbrooding is an advantage for the hobbyist, too. He immediately knows when a female is "carrying" and all he has to do is to net it and place it in a tank of its own - if he wishes to raise the whole brood. A carrying female is easily identified: it will refrain from eating or will carefully eat very small quantities, it will occasionally look like "chewing" (actually she aerates its fry) and will try to avoid fights and quarrels. Even very active species will look a bit milder and far less active - sometimes you may even see it staying in a dark part of your tank or close to the bottom, behind the filters etc. It will usually keep the fry for 3 weeks and then release them. Please take note that the duration of the carrying term depends on the water temperature. Thus, at 24oC the duration may reach 4 weeks while at 30 degrees it may be as short as 17 days. You should always take this factor into account when making your calculations otherwise you may end up with the fry released in the main tank. In all cases, the fry is completely developed when released. Some species (notably Labidochromis caeruleus, the electric yellow labido) use to carry much longer. It is not rare for these species to carry for more than 30 days (I have personally witnessed a 41 day carrying period).
You should keep in mind that some species are "seasonal" spawners. Thus, my Sciaenochromis fryeri will start spawning in the end of May and will do so three times (till the end of September) every year. It will not spawn during the rest of the year. Age plays an important role on the frequency of spawning. The fish will spawn regularly for some years and then, as it gets older it will spawn less frequently. The size of the brood increases as the fish matures. Usually the first couple of attempts will not be successful but then nature will find its way. In some species (very common among the haps), the male takes considerably longer to reach sexual maturity than the female. This will also lead to some unsuccessful spawns.
Some fish will not spawn if the environment is not appropriate. Haps (especially large species) do not feel very well in crowded tanks and even if they try to spawn, other haps (natural predators) will lurk around to interrupt the spawning and eat the fry. Thus, you may see a spawning pair but not a carrying female after that. The presence of an aggressive hyperdominant species (especially in mbuna tanks) may prohibit milder species from spawning at all. It is not rare to see many species spawing on the spot once a hyperdominant male is removed from the tank. After removing a 14 cm male Melanochromis auratus and a 15 cm male Melanochromis chipokae from my tank, I observed five carrying females within one week, females that had never spawned before. In conclusion, the fact that a pair will not spawn may just mean that the conditions or the nature of the fish is such that will not allow it to spawn in that particular tank. There are many more issues related to this matter. It seems that the females in nature choose their mate. They will refuse to spawn with an inferior male and they select the one that looks "promising" by the size and shape of the nest (spawning pit) it managed to built - among other factors. This is very rarely seen in the artificial environment of the tank in which the female doesn't have any other options and building a pit is usually not an option for the male. However, some times a female will cross breed with a male from another species even if a male of its own species is present in the tank.
Some people use to "strip" their females. This is not the natural way to go and should only be done if the mother is sick or has a long history of unsuccessful carriages - and you badly need the fry. Stripping a female may result in the release (spitting) of immature fry with the yolk sacs still attached, an easy meal for the rest of the tankmates. It may also result in injuring or stressing your female too much. Even if you are successful in stripping your female, the females raised this way (from stripped mothers) have a much longer history of spitting or swallowing. It is now widely accepted that mouthbrooding is not only a way to protect but also the best way to aerate, feed and "educate" the fry. Nobody can replicate that! Moreover, the stripped females give fry that are more prone to disease.
Netting them may sometimes be easier said than done. Chasing a small sized female, which hides under every rock in your tank until you remove all of them, is not a rare situation. Things are a bit better with haps, mainly because of their larger size. One thing that has to be noted here is that haps should be handled more gently than mbuna. Some haps will immediately spit their fry if stressed too much. This may happen in your net - which is good news - but it may also happen out of it (which is good news for the other haps but not for you). It is always better to use two big nets (that are at least 1,5 times wider than the overall length of your fish) one to chase the fish and the other one to catch it. The method that works best for me is to leave one of the nets still and "guide" the female in it. Then - when the fish is almost in the still net - with a quick move I net her. Once netted be as gentle as possible with it. It is even better to leave the nets for 10 minutes or so in the tank (so the fish get somehow used to them) and then try with gently moves to net the female. You will be amazed to see that sometimes you may net a female with very gentle moves and the least of stress to it. Among the species I have spawned the worst spitters are Cyrtocara moorii and Nimbochromis livingstoni. In contrast, my female Sciaenochromis fryeri will stay almost motionless, waiting to be netted. There are no rules on this one. One of the most experienced hobbyists I know of, has the hell of a time every time he has to net his female fryeri. He always ends up tearing apart his tank or he just quits the game. You can always see all size of Sciaenochromis fryeri fry swimming in his tank - a sign of failed attempts to net the female.
Own tank vs. the main show tank? Well, it depends. Usually, most hobbyists want to be able to see the way the female gradually allows the fry to stay out of its mouth or the way it will take them back when the enemy (you) approaches the tank. If mortality rate is the only thing that interests you then the separate raising tank is a must. However, even if the fry is released in the main tank, some of it will survive. A mortality rate of approximately 5% in an overstocked mbuna tank with few hiding places is the most you can expect. However, you may be able to get a 30% survival rate in an understocked mbuna tank with plenty of hiding places correctly built and placed. If you have such a tank, not removing the carrying female is always a good option. In a tank with adult piscivore haps things are far worse. In such a tank (even with hiding places) the survival rate is always very low. It usually is less than 1%. This is because unlike the mbuna tank, in which fish reaching the age of 4 months (sized 3-4 cm) will probably grow to maturity, in a tank housing large piscivores, the danger is always there. Even fish sized 8 cm may be eaten on the spot. Unfortunately, haps don't grow much quicker than mbuna, so they must reach the age of 1 year before they are safe. In all cases, the more broods are released in the same tank the lower the survival rate, because the best hiding places will already be occupied so the newly released fry will only find very risky spots to hide. Just a quick note : in a raising tank, the most efficient fry killer is a strong filter which will trap the fry. A way to deal with it effectively is to wrap the filter in nylon mesh. The same precaution should be taken when changing the water of the raising tank or vaccuuming the gravel in the main tank.
Plastic hatching compartments or artificial plexiglass dividers are just another way to keep fry of more species in the same tank volume. However, this has some disadvantages. Keeping them too crowded (if the species allows for that) results in a reduced growth rate, unless you follow the discus raising procedures = huge water changes as often as possible. The floating nests will allow you to keep more fry but they will take centuries to grow. On top of that, the hygiene of the water is very poor no matter how hard you try to improve it and the outbreak of a disease, if it happens, will have devastating effects on the population. This is because the water flow in the floating nests is far less than needed and the fish is very crowded so the pathogen will not need to travel a lot to find is next victim. Usually, I just select a few species to keep and raise their fry and I let the others in the main tanks. You can always mix fry from two different species as long as their age is more or less the same and their melanin pattern is different. Otherwise you will have a big problem when you will have to tell which is which. Thus, it is a good idea to keep species with blotches (Nimbochromis fry) with other species with bars (Protomelas taeniolatus or Cheilochromis euchilus - see photos below). It is definitely not a good idea to keep the P.taeniolatus fry with the C.euchilus fry in the same tank. While young (less than 6 months) their main difference is their color (silver vs. gold) but you can't possible rely on that, not can you wait 15 months to be sure.
Growth rate is a complicated matter, which is related to a lot of factors. Among them, the key issues are water temperature, feeding habits (frequency and type of food), frequency of water changes, filter capacity, filter precautions, hygiene precautions and maintenance (e.g. dead fish is removed on the spot, fish waste is regularly removed, filters are regularly cleaned etc.). The higher the temperature the quicker the fry will grow. This is mainly because their metabolism in increased and has the drawback of a reduced life span and an increase in aggression levels. When we discuss the temperature issue one needs to have in mind that this should not reach very high levels. The higher the temperature the less oxygen is dissolved in the water which may kill (suffocate) your fish. On top of that, different species will tolerate higher temperature in different ways. Thus, while discus will thrive at temperatures exceeding 30oC, cichlids from Lake Malawi will not feel comfortable at any temperature over 29oC while their Tanganyikan counterparts will tolerate even lower temperatures (28oC at maximum). Frequent feeding, frequent water changes, excellent hygiene and tank space all have a positive effect on the growth rate. If your raising tank is not permanently working, an ammonia peak will definitely occur and kill all the fry unless you perform large and frequent water changes (usually I change about 85-90% of the water every week). This must be accompanied by regular ammonia testing to ensure that the biological filter works (ammonia levels drop) before you can gradually decrease the frequency of water changes. The fact that normally you have to feed very frequently (5-6 times daily) makes this precaution a must. Even a partially established filter may not protect your fry under this feeding schedule.
Type of food. Although I never bothered to raise my own daphnia or artemia (too little time to do that, too), it seems that this is the best food for fry (and it makes sense). I use commercially available foods and I just move from the "baby" to the "growth" and finally the "adult" versions as the fish grow. Well, my fish grow fairly fast and it seems that the growth rate is comparable to that of fry raised on fresh food. Usually, most of the fry will be able to feed on the same food the adults take when they are six months old. In small species it may take a bit longer. If you want to save on food, you can always crush the flakes of the parent's food into very small pieces which the fry will be able to eat.
As they grow up more problems arise and the hobbyist should be alerted when he sees the first signs. Aggression and cannibalism are the most common problems that can be observed in fry from different species. This is generally the issue with fry of non-mbuna cichlids. The Nimbochromis genus (venustus, polystigma, livingstoni) is renowned for uneven growth within the same brood. The larger fish will definitely eat its brothers or sisters sooner or later. You have to separate them according to their size if you observe the tension being built up in the tank. Aggression is the next issue and, since we are talking about Africans, this is the rule. However there are grades of aggression. Thus, Sciaenochromis fryeri or Cyrtocara moorii males will grow for 7-8 months before any serious problems arise (sometimes even 12 month old fry will still behave in a mild way). It goes without saying that the most crowded the raising tank the less the aggression is but in this case you should keep in mind the drawbacks of crowded tanks. Melanochromis species are far less tolerant and males start to be intolerant at the age of 5-6 months - especially if crowded. With Haplochromis nyererei things are far more difficult. A pronounced aggression and intraspecies intolerance between the males is evident from the age of 2-3 months and the first deaths occur before the age of four months. Keeping more than 5-6 males in a 45 liter tank is impossible. You have to divide them in more tanks. I have found out that, until the age of six months, not more than 3 males / 45 liters can coexist. After than point you have to reduce the males to 2/40 liters. Again, there are no rules to follow.
Parental care. This is another issue which needs to be addressed since not all parents show the same care for their young. Thus, while in some shell swelling cichlids of Lake Tanganyika the fry can stay with the parents and participate in the raising of subsequent broods (thus creating a large colony) in other species the fry will be eaten by the father or even the mother. Moutbrooding females have the exclusive responsibility to raise the fry. The males do not participate in this procedure and are a constant threat for the fry (especially for predatory species). After being released the fry is taken care for some time (ranging from several days to a few weeks) and then the female will leave them on their own. After this point the fry is regarded as good by any member of the tank. Bear in mind that most loaches are extremely capable of eating the fry in the dark and can keep control of the fish population in your tank. In contrast, in New world cichlids both parents usually raise and protect the fry. This should be taken into account when you have to make decisions concerning the future of your fry. Usually, if you want to raise the fry of mouthbrooding cichlids it is best to remove the mother and let her release in its own tank. When you see that she doesn't allow the fry to enter its mouth again, it is time to return it to the main tank. This is also a point which should be very well thought of. In some species (Tropheus, for example), removing the female is easy but returning it to the main tank is a risky decision as it may be harassed to death by the rest. The same is true for some Melanochromis species (M. auratus and M. chipokae) in which case other females may chase the weakened mother to death. I have had no problem in removing and returning my Melanochromis auratus and chipokae in the main tank but I know of many people who have lost their females shortly after their return in the main tank.
How long to keep? Should you sell or keep some? These are some of the questions asked by some hobbyists. If your final goal is to sell them then you have two options. For a quick turnover you should try mbuna or other small fish, which have vivid colors at any age. The pitfall here is the price you will get. Most people keep mbuna who happen to be very prolific too, so the price you will get is very low. On the other hand, you can sell them easily at 4-5 months. Haps are exactly the opposite. They have much larger broods (more than 80 in most cases) but the fry has no color (with some exceptions like Cyrtocara moorii) and it takes at least 7 - 10 months for the males to develop it. Still, females don't look that attractive and some hobbyists prefer a "male" only aquarium. The advantage is that some species are quite "rare" but this in turn means that less hobbyists will want a 30+ cm monster in their small tanks. So, it is up to you really. If you have plenty of tanks this will not be a problem, since you can successfully raise all the fry you can get. However, in most cases, the tank space is limited so, in order to raise the fry of one species you must first empty the tank from the previous fry. This is really a headache. More often than not, your precious pair will decide to spawn exactly two days after some other species released 60+ fry in the last empty tank you had.
There are some precautions and notes that should be taken into account when spawning your fish. First comes hybridization.
Hybridization is the spawning of two specimens, which belong to different species. In African Cichlid tanks this usually takes place between members of the Aulonocara genus. Females of most species of this genus look almost identical and it is very common for a male of one species to spawn with a female of a different species. This will inevitably happen if the female doesn't have a male of her own species in the tank or her male is too small or weak to defend its position as a spawning partner. It may also happen in the presence of her "own" male. It is generally advised not to keep two different Aulonocara species in the same tank. There have been reports of hybrids from other species, even species which differ greatly both in size as well as shape and melanin pattern (Cyrtocata moorii with Nimbochromis venustus for instance). The reasons that lead to hybridization are not very clear. It has been said that this may also happen in nature (to a far lesser degree). It was already mentioned that some studies indicate that usually females are "choosy". The hobbyist should pay attention and, if hybridization takes place he should discard the fry or use them as feeder fish. Hobbyists should know that hybrids may be fertile for at least two generations and produce a big number of offspring which will be offered in the hobby and - eventually - back to him.
Genome redistribution is another issue that needs to be discussed in this article. I feel that we should briefly go through some basics before we address this issue. All living organisms have a specific number of chromosomes, which is a characteristic of the species. Genome comes in sets of two chromosomes, each chromosome of a set carrying information for the same things (functions or characteristics) in the same region. If both chromosomes carry the same information for a specific characteristic or function then the organism is called a homozygote. If they carry different information about the same characteristic they are called heterozygotes. A characteristic may be the color of the dorsal fin, the final size, everything that characterizes the fish (genotype). Genotype could be described as all the characteristics described (contained) in a fish's genome - the inherited information. This includes all information whether expressed or not. The way the fish will finally look has to do with other environmental parameters, which may or may not allow the genotype to be finally shown, as it should. Thus, although the genome specifies that a fish should grow to 30 cm, there are some environmental factors (e.g. space of tank, water parameters, serious diseases, kind of food, food quantity etc), which may not allow the fish to reach this size. So the fish may only reach a final size of 20 cm. The final characteristics of the fish create the phenotype (how the fish finally looks). Sometimes, organisms carry a "defected" chromosome (mutated) which may not be expressed (recessive chromosome) but is still part of their genome. When both chromosomes carry the same "defect" then this characteristic is expressed. Since it is a recessive characteristic, most usually it is an unwanted one. As said, the only way it can be expressed (thus becoming part of the fish's phenotype) is that both parents have at least one of these "mutated" chromosomes (since the fry will have to get one defected chromosome from each parent). The possibility to produce such fry is very high when we breed brothers with sisters or sons (or daughters) with their parents. This is because both parents carry the same genome. If we want to avoid passing this information onto the fry one of the parents should carry a different (not related) genome. However, when you acquire captive bred specimens you can't tell if the female and the male are not from the same parents. Most local fish shops get their fish from the same breeders (hobbyists or big hatcheries) therefore the only way to ensure you will not redistribute the same genome is to make sure that one of the parents is a wild caught specimen. This is a very good reason to look for wild caught species. I am personally against the collection of specimens from the natural environment. This is especially so for cichlids from the African Rift Lakes which readily reproduce in captivity. However, the need to redistribute the genome is really important, although it should be understood that you don't need both parents to come directly from the Lake.
This article doesn't have the ambition to teach you everything there is to know about raising your fry. Since you do have fry to raise you are already experienced and you know - at least - the basics. What this article aims at is to give you some information that is usually overlooked or not taken into account.
The Author suggests that all hobbyists should visit the website of Ron Coleman, "The Cichlid Research Homepage" in order to get a complete view of cichlid spawning.
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